Sonic World Adventure (ソニックワールドアドベンチャー Sonikkuwārudoadobenchā?) is a two chapter story that was featured in Dengeki Nintendo DS, which is a Japanese gaming magazine published by ASCII Media Works (formally MediaWorks). It was part of the promoting campaign for Sonic Unleashed in Japan and it loosely follows the plot since Sonic's transformation into the Werehog due to Eggman's scheme and later adventures with Chip.
It starts as Sonic is finishing his transformation to the Werehog. Eggman gloats about having payback for all the times Sonic has messed up his plans. Sonic challenges him to try how many times he wants, but he will never let him win. After this, he quickly escapes the room by breaking through a wall. Eggman calls for his robots to catch him after recovering from the surprise. Sonic falls to Earth, amazed by his new found strength, and promises he'll thank Eggman later for it.
Sometime later, Sonic and Chip are heading towards a shrine. Chip retorts he's hungry and Sonic agrees to stop at the next village (from the layout, it seems to be Apotos) and perhaps someone will know him there as well. Chip quickly rushes ahead, screaming for ice cream.
At the village, an ice cream vendor (very different in design from the game one) promotes his products. Chip shows up and demands ice cream rabidly, and he's so eager that he ends up destroying the whole shop. Sonic arrives, in time to hear Chip's desperation of not finding any ice cream and the ice cream's vendor's crying for his lost shop. Sonic, thinking to himself that it was actually Chip who broke the store, tells them to shut up and promises to do something about it.
Sonic and Chip leave to find materials for the repairs. Chip is very happy to help but ends up finding food instead of construction material. Sonic scolds him, saying it's not the time to look for food but Chip is already picking up apples for the future ice cream, and even though Sonic scolds him some more, Chip manages to find a strawberry. Sonic kicks him in the head and leaves annoyed.
He runs into a group of Egg Fighters but he defeats them quickly and stylishly. Chip shows up and comments that they've collected a decent amount of construction materials, referring to the metal scrap lying around. Sonic likes this idea and they quickly return to the village.
They present the new shop to the vendor. Since they've used robots, the shop now automatically serves customers and even speaks to them. Chip very happily says he wants to be the first customer. He approaches the shop, which welcomes him and shoots him down. The shop quickly goes after Sonic and the ice cream vendor as well.
Sonic has finished defeating a group of Egg Fighters, but there are more to destroy. Chip lands on his hand and tells him night has almost come and he'll transform soon. Sonic quickly destroys the rest of the Egg Fighters and runs with Chip hanging to his quills. Chip tells Sonic that he thought of him as a scary but gentle person when they first met. This leads to a flashback.
Sonic is falling through the atmosphere and splatters on the ground. He looks up and says he now knows how it's like to fall from space without Tails to catch him. Sonic then notices Chip laying on the ground and asks him if he's alright. Chip murmurs he can't eat anymore and opens his eyes. Sonic smiles creepily and Chip freaks out, quickly shoving his paw in his eyes and running away to hide behind a stone, yelling that he's not tasty. Sonic looks a bit shaken, but then tells him his name and asks for his. Chip wonders about this and then says something fell from the sky and hit him, which knocked him unconscious and that's why he doesn't remember anything. Sonic wonders if it was him and reassures Chip that he will help him and perhaps maybe someone around knows who he is. Suddenly, the sun shines and Sonic transforms to his regular form. Chip is very surprised and asks him how he changes. Sonic tells him he doesn't know, it just happened when the sun came up. He then tells Chip they should be off looking for his memories and Chip happily agrees with him. The flashback ends.
Sonic looks up at the moon and notices he has transformed into the Werehog. He looks at the Egg Fighters still following him and quickly defeats them with his new transformed arms. There is one left, ready to shoot him, but Sonic quickly stretches his arm to punch it, commenting it's all too easy.
Chip celebrates Sonic's strength and happily tells him they can now go look for his memories, as it was all Sonic's fault he lost them in the first place. Then he continues his obnoxious behavior, ranting about ice cream some more and Sonic looks crestfallen at having his fault in the whole ordeal rubbed in his face like that.